Modifiers for iron carbon alloys

ABSTRACT

A modifier, based on calcium and silicon, for iron-carbon alloys, also comprising magnesium, rare earth metals, barium, strontium, yttrium, lithium scandium, rubidium, not counting occasional or indispensable constituents, the ratio of the constituents being chosen so, that the modifier can with equal success be applied to both cast-irons and steels, no nonmetallic impurities being formed in the body of metal.

United States Patent 1 1 Voloschenko 1 Oct. 2, 1973 1 MODIFIERS FOR IRON-CARBON ALLOYS 22 Filed: July 9,1970

21 Appl. No.: 53,673

[52] U.S. Cl. 75/130 AB, 75/129, 75/134 S [51] Int. Cl. C22c 31/00 [58] Field of Search 75/130 A, 130 AB, 75/130 B, 134 S, 129, 134 S [56] References Cited UNITED STATES PATENTS 2,676,097 .4/1954 Strauss 75/130 A X 2,750,284 6/1956 Ihrig 75/130 AB 2,762,705 9/1956 Spear 75/130 AB 2,805,150 9/1957 Strauss... 75/130 A X 2,823,989 2/1958 Deyrup 75/130 B X 3,328,164 6/1967 Muhlberger... 75/130 AB X 3,336,118 8/1967 Newitt l 75/130 A X 3,396,777 8/1968 Reding... 75/130 A X 4/1969 Kallenbach 75/134 A X 12/1970 Turillon 4. 75/130 B X OTHER PUBLICATIONS I-Iampel, Clifford A., Rare Metals Handbook, Second Edition, Reinhold Publishing Corp., London, 1961, p.

Primary ExaminerL. Dewayne Rutledge Assistant Examiner-J. E. Legru Att0rney-Holman & Stern [57] ABSTRACT A modifier, based on calcium and silicon, for ironcarbon alloys, also comprising magnesium, rare earth metals, barium, strontium, yttrium, lithium scandium, rubidium, not counting occasional or indispensable constituents, the ratio of the constituents being chosen so, that the modifier can with equal success be applied to both cast-irons and steels, no nonmetallic impurities being formed in the body of metal.

10 Claims, No Drawings MODIFIERS FOR IRON-CARBON ALLOYS The invention relates to metallurgy, and more specifically to modifiers for cast-irons and steels (iron-carbon alloys).

Known in the art is the use of modifiers in smelting cast-irons. This increases their strength two to five times as compared to non-modified cast-irons.

The increase of strength is due to the fact that modifiers promote formation of spheroidal graphite in castiron.

Widely employed at present are cast-iron modifiers consisting of alloys, such as nickel-magnesium, magnesium-ferrosilicon, magnesium-copper, magnesium-nickel-rare earth metals, as well as magnesium per se.

A general disadvantage of the mentioned modifiers consists in the fact that their employment entails formation of nonmetallic inclusions resulting from the magnesium in said compositions, or when used alone, yields compounds with sulphur and oxygen.

This causes nonuniform structure of cast-iron, and reduces its strength. I

Also known in the art is the employment of rareearth metals alone as cast-iron modifiers. Just as in the above-mentioned cases, this involves nonmetallic formations in the cast-iron. Besides, these modifiers are in themselves expensive.

To prevent the occurrence of .said nonmetallic formations, there have to be employed additional production operations: previous desulphuration of the castiron, overheating it to high temperatures, application of such fluxes as cryolite, soda ash, etc., these operations making the manufacture of high-strength cast-irons more complex and costly.

Besides, when magnesium alone, or the above-cited compositions comprising magnesium are used as modifiers, there occur strong flashes of magnesium, and splashes of liquid cast-iron. This forces the use of special protecting devices and arrangements, such as sealed ladles, autoclaves, protective chambers, etc. And this again makes the production of high-strength cast-iron more complicated and more costly.

Also, in case cast-iron includes such admixtures, as arsenic, titanium, bismuth, tin, lead, and some other elements, it is generally difficult securing stable formation of spheroidal graphite, i.e., obtainment of highstrength cast iron with the aid of the above-mentioned modifiers.

Also known in the art are cast-iron modifiers consisting of mechanical mixtures based on calcium and silicon, namely mixtures of silico-calcium with magnesium chlorides and fluorides, as well as with chlorides and fluorides of rare-earth metals.

A disadvantage of these modifiers is the fact that they cannot secure stable formation of spheroidal graphite in cast-iron. In addition, chlorides of magnesium, cerium, and other modifier metals are hygroscopic, which requires their special packing and storaging.

A further disadvantage of said modifiers is the abundant smoking during the modification of cast-iron.

Known in the art are other cast-iron modifiers, comprising magnesium, calcium, and alloying elements, such as nickel, copper, manganese, etc.

Most widely used are modifiers of this kind with the following compositions, in percent:

Mg-30, Ca-20, Si-39, Al-2.5, Mn-0.5, Te-17, or

2 Ca-22, Si-50, Li 6-15, Mg 2-4, Nli 13-20.

The disadvantage of these and similar modifiers is their high cost, as well as the complexity of their production, since the introduction of the alloying metals, i.e., of Ni, Cu, etc., requires performance of additional operations of melting and mixing the constituents.

The conventional modifiers are of little use for steel modification, since steels have a higher melting point (by -350C), than cast-irons, while most of the conventional modifiers comprise a large amount of magnesium. Introduction of these modifiers into molten steels may cause such strong flashes and splashes, that their use becomes practically impossible.

Modifiers with a relatively small amount of magnesium (up to 10 percent) usually have significant proportions of alloying constituents (nickel, copper, manganese, chrome), the introduction of which will substantially change the properties of the modified steels.

An object of the invention is to eliminate the disadvantages of the conventional modifiers.

The basic object of the invention was to find a modifier of such a composition, that would not have the disadvantages of the above-described conventional modifiers, and could also be used with equal succes for modifying steels.

With this object in view, a modifier based on calcium and silicon has been found, which, according to the invention, comprises, in weight percent: calcium from 6 to 30, silicon from 51 to 66, magnesium from 0.2 to 10, rare-earth metals from 0.1 to 12, bariumfrom 0 to 12, strontium from 0 to 12, yttrium from 0 to 10, lithium from 0 to 12, scandium from 0 to 10, not counting occasional or indispensable constituents.

The most effective modifiers are those, whose compositions vary within the following limits (in weight percent): calcium 6-24, magnesium 5-10, rareearth metals 2-10, strontium 0.2-6, lithium 0.1-5, barium 2-8, yttrium 0.1-6, scandium 0.1-6, silicon 51-66.

For alloyed cast-iron with high sulphur content, as well as in the production of castings of large weight, most advisable are modifiers, whose composition lies within the following limits (in weight percent): calcium 7-18, magnesium 6-9, rare earths 3-5, strontium 1-4, lithium 1-3, barium 3-6, silicon 51-64.

To modify cast-iron with a sulphur content of up to 0.05 percent, as well as carbon and low-alloyed steel, and high-manganese steel, the use of modifiers with the following composition (in weight percent) is recommended: calcium 6-16, magnesium 2-5, rare earths 5-9, barium 2-5, silicon 53-65.

Modification of cast-iron with a. sulphur content of up to 0.12 percent, as well as of Hatfield and other steels, is advisable to be done with modifiers having the following composition (in weight percent): calcium 7-18, magnesium 2-5, rare earths 7-10, silicon 56-65.

For modification of cupola irons with a low melting point (l300-1370C) and with a high sulphur content (0.10-0.13 percent) most advantageous are modifiers of the following composition (in weight percent): calcium 7-18, magnesium 6-9, rare earths 3-4, silicon 56-65.

To modify mediumand high-carbon steels, as well as alloyed steels and low-sulphur cast-irons containing not less than 0.004 percent of sulphur, it is advisable to use modifiers with the following compositions (in weight percent): calcium 6-16, magnesium 2-4, rare earths 1.5-5, barium 4-6, lithium 1.5-4.0, silicon 51-65.

In modifying highor complex-alloyed steels, it is most advisable to employ modifiers whose composition lies within the following limits (in weight percent): calcium 6-20, magnesium 0.2-3, rare earths 3-5, barium 3-6, lithium 2-5, strontium 2-6, yttrium 1-3, scandium -l-3, silicon 51-66.

Modification of cast-irons with a sulphur content of up to 0.08 percent, as well as of carbon and alloy steels, acting under abrasive wear and alternating loads, should most adventageously be done with a modifier of the following composition (in weight percent): calcium 6-15, magnesium 0.5-4, rare earths 4-7, rubidium 1-5, silicon 51-66.

Given below is a detailed description of the invention illustrated with particular examples of modifier compositions, according to the invention.

Modifiers made according to the invention, whose composions vary within the following limits (in weight percent): calcium 6-30, silicon 51-66, magnesium 0.2-10, rare-earth metals 0.1-12, barium -12, strontium 0-12, yttrium 0-10, lithium O-12, scandium 0-10, rubidium 0-10, can be used with equal succes for all cast-irons, including those with high content of sulphur, titanium, arsenic, tin, lead, nickel, copper, as well as for ordinary and alloy steels. The presence of strontium barium, lithium, scandium, rubidium, yttrium in the modifier improves its refining and modifying action on cast-iron and steel.

The modifiers can be employed in the form of alloys or mechanical mixtures. Their employment in the form of alloys is most advantageous, since their production in such form is cheaper, while the quality of modification is the highest.

The modifier is introduced into liquid iron-carbon alloy in a crushed form.

In this case the heat losses in the modified metals are reduced, and thee extent of the modifier absorption thereby is increased.

Crushing can be done' in ordinary crushers employed in foundry and other metallurgical shops.

The modifiers are in most cases used with fluxes, mainly fluorite or fluor spar, wherewith they are in a mechanical mixture.

The ratio between the modifier and the flux is of conventional order, being respectively 3:1.5-O.5.

Modifiers according to the invention make it possible to obtain castings from high-strength cast-irons and steels having no nonmetallic inclusions and no chill, and with a smaller amount of pouring defects (shrinkage porosity, shrinkage cavities), as compared to castiron and steel castings obtained with the prior art modifiers.

In addition, introduction of these modifiers into the metal to be modified does not require any special equipment,.such as autoclaves, sealed ladles, protective chambers, etc., cince these modifiers cause no flashes or splashes during their introduction into the molten metal.

Shown below are examples of composition of the modifiers, and of their application in various alloys.

EXAMPLE 1 The modifier has the following composition, in weight percent:

up \omwuiwuusom After treating 300 tons of cast-iron comprising 0.15 percent of sulphur, 0.15 percent of titanium, 0.1 percent of bismuth, with the modifier of the said composition, there was obtained a high-strength iron casting weighing 22 tons with a wall thickness of 50 to 150 mm. The form of graphite in all the sections of the iron of the casting was spheroidal.

There were no shrinkage porosity, shrinkage cavities, or nonmetallic inclusions. Speciments cut out from the body of the casting showed a tensile strength of 52-58 kg/mm an elongation of 10 to 15 percent, and a Brinell hardness of 179-191 l-lB.

EXAMPLE 2 The modifier has the following composition, in weight percent:

calcium magnesium rare earths strontium lithium barium silicon 6 Vat-Noumea EXAMPLE 3 The modifier has the following composition, in weight percent:

calcium 9 magnesium 3 rare earths 9 barium 4 silicon 5 6 After modification of carbon steel with a carbon content of 0.23 percent a casting was obtained weighing 3.2 tons. The mechanical properties of this steel obtained no speciments cut out from lug bosses, were as follows: tensile strength 48 kglmm elongation 28 percent, impact ductility 19 kgmt/cm On treatment with the same modifier of alloy steel comprising 0.15 percent of chrome, 0.26 percent of nickel, a casting was obtained with a weight of 1.9 tons.

The properties of the modified steel were as follows: tensile strength 69 kg/mm, elongation 18 percent, impact ductility 16 kgmt/cm 1 A casting of 70 tons was produced from high-strength cast-iron treated with said modifier. The mechanical properties of samples were as follows: tensile strength 62 kg/mm elongation 3 percent, hardness 261 RE. No non-metallic inclusions were found in the casting.

EXAMPLE 4 Lambcalcium magnesium rare earths silicon 6 The modifier was used to treat cast-iron containing 0.11 percent of sulphur. From such iron castings for lathes were made. The weight of castings was up to 100 kg., the wall thickness from 5 to 40 mm. Nonmetallic inclusions in the castings were completely absent, the graphite form was only spheroidal. No structurally free carbides were observed in castings with varying wall thickness. Without any heat treatment the castiron has the following mechanical properties:

bending strength 125-135 kg/mm tensile strength 62-70 kglmm elongation 2.54 percent hardness HB 241-269 Experiments in treating with said modifier a Hatfield steel having 13 percent of manganese showed a sharp finening of grain (2-4 times) and an increase in wear resistance, as compared to unmodified steel. The quality of the castings (with regard to shrinkage defects) was considerably raised.

EXAMPLE 5 The modifier has the followingcomposition, in weight percent:

calcium magnesium 9 rare earths 3 silicon 64 tensile strength 52-58 kg/mm elongation 3.2-4.3 percent hardness HB 229-241 EXAMPLE 6 The modifier has the following composition, in weight percent:

calcium rare earths magnesium barium lithium silicon iron aluminium mf Nuts-cam 25.5 indispensable 2.0 constituents The modifier was applied to cast-iron with 0.03 percent of sulphur. 90 tons of liquid cast-iron was modified. Before pouring, the modified cast-iron was kept in the ladle for 3 hours, whereupon castings were made with a weight of from 2 kg to 26 t.

In all the casting the graphite shape was spheroidal. and no nonmetallic inclusions were found.

Said modifier was used to treat a carbon steel comprising 0.67 percent of carbon. As a result of modification, in castings weighing 80 kg columnar crystals were completely eliminated. A fine-grained structure was obtained. The strength and plasticity of this steel rose by about 40 percent, as compared to unmodified steel. Impact ductility was particularly raised.

EXAMPLE 7 A modifier comprising, in weight percent:

calcium magnesium rare earths barium lithium strontium yttrium scandium silicon was applied to a chrome-nickel-m olybdenum steel.

As a result of modification, the macrostructure of the steel significantly improved, and the content therein of gases and nonmetallic impurities was reduced more, than twice. The strength rose by 25-30 percent, and the impact ductility by 40 percent, as compared to unmodified steels.

The said modifier was applied to an austenitic steel, comprising 18 percent of chrome, 9 percent of nickel, and 0.5 percent of titanium. After modification, test castings weighing 100 kg showed a not less than double increase of wear resistance.

What we claim is:

1. An iron-free modifier based on calcium and silicon, for iron-carbon alloys, consisting essentially of, in weight percent: calcium from 6 to 30, silicon from 51 to 66, magnesium from about 0.2 to about 9, rare-earth metals from 0.1 to 12, barium from 0 to 12, strontium from 0 to 12, yttrium from 0 to 10, lithium from 0 to 12, scandium from 0 to 10 and rubidium from O to 10.

2. A modifier as claimed in claim 1, comprising, in weight percent: calcium 6-24, magnesium .5 to 9, rare earths 2-10, strontium 0.2-6, lithium 0.1-5, barium 2-8, yttrium 0.1-6, scandium 0.1-6, silicon 51-66.

3. A modifier as claimed in claim 1, comprising, in weight percent: calcium 7-18, magnesium 6-9, rare earths 3-5, strontium l-4, lithium l-3, barium 3-6, silicon 51-64.

4. A modifier as claimed in claim 1, comprising, in weight percent: calcium 6-16, magnesium 2-5, rare earths 5-9, barium 2-5, silicon 53-65.

5. A modifier as claimed in claim 1, comprising, in weight percent: calcium 7-18, magnesium 2-5, rare earths 7-10, silicon 56-65.

6. A modifier as claimed in claim 1, comprising, in weight percent: calcium 7-18, magnesium 6-9, rare earths 3-4, silicon 56-66.

7. A modifier as claimed in claim 1, comprising, in weight percent: calcium 6-16, magnesium 2-4, rare earths 1.5-5, barium 4-6, lithium 1.5-4.0, silicon 5l-65.

8. A modifier as claimed in claim 1, comprising, in weight percent: calcium 6-20, magnesium 0.2-3, rare earths 3-5, barium 3-6, lithium 2-5, strontium 2-6, yttrium 2-3, scandium l-3, silicon 51-66.

9. A modifier as claimed in claim 1, comprising, in weight percent: calcium 6-15, magnesium 0.5-4, rare earths 4-7, rubidium l-5, silicon 51-66.

10. A method for modifying cast iron comprising adding an effective amount of the modifier of claim 1 to molten cast iron. 

2. A modifier as claimed in claim 1, comprising, in weight percent: calcium - 6-24, magnesium - .5 to 9, rare earths - 2-10, strontium 0.2-6, lithium - 0.1-5, barium - 2-8, yttrium - 0.1-6, scandium 0.1-6, silicon - 51-66.
 3. A modifier as claimed In claim 1, comprising, in weight percent: calcium - 7-18, magnesium - 6-9, rare earths - 3-5, strontium - 1-4, lithium - 1-3, barium - 3-6, silicon - 51-64.
 4. A modifier as claimed in claim 1, comprising, in weight percent: calcium - 6-16, magnesium - 2-5, rare earths - 5-9, barium - 2-5, silicon - 53-65.
 5. A modifier as claimed in claim 1, comprising, in weight percent: calcium - 7-18, magnesium - 2-5, rare earths - 7-10, silicon - 56-65.
 6. A modifier as claimed in claim 1, comprising, in weight percent: calcium - 7-18, magnesium - 6-9, rare earths - 3-4, silicon - 56-66.
 7. A modifier as claimed in claim 1, comprising, in weight percent: calcium - 6-16, magnesium - 2-4, rare earths - 1.5-5, barium - 4-6, lithium - 1.5-4.0, silicon - 51-65.
 8. A modifier as claimed in claim 1, comprising, in weight percent: calcium - 6-20, magnesium - 0.2-3, rare earths - 3-5, barium - 3-6, lithium - 2-5, strontium - 2-6, yttrium - 2-3, scandium - 1-3, silicon - 51-66.
 9. A modifier as claimed in claim 1, comprising, in weight percent: calcium - 6-15, magnesium - 0.5-4, rare earths - 4-7, rubidium - 1-5, silicon - 51-66.
 10. A method for modifying cast iron comprising adding an effective amount of the modifier of claim 1 to molten cast iron. 